Combustion brilliancy control



Jan. 16, 1951 H. T. SAWYER 2,538,428

COMBUSTION BRILLIANCY CONTROL SYSTEM Filed April 25, 1946 2 Sheets-Sheet 1 INVENTOR.

HAROLD T. SAWYER 1951 H. T. SAWYER 5 COMBUSTION BRILLIANCY CONTROL SYSTEM Filed April 25, 1946 2 Sheets-Sheet 2 INVENTOR.

HAROLD T. SAWYER FIG 4 BY Patented Jan. 16, 1951 COMBUSTION BRILLIANCY CONTROL SYSTEM Harold '1. Sawyer, Seattle, Wash, assignor to Bailey Meter Company, a corporation of Delaware Application April 25, 1946, Serial No. 664,753

My invention relates to control systems and particularly to providing method and apparatus for controlling variables in the operation of power producing or utilizing apparatus responsive to a variable condition of the operation.

'One object of my invention is to provide a control of one or more of the elements of combustion supplied to a fuel fired furnace for liberatin heat. Preferably the rate of supply of one or more of such elements of combustion is controlled at least in part in accordance with a determination of brilliancy of the furnace. The said brilliancy may be of the flame, the gaseous products of combustion, the walls of the furnace or of a fuel bed in the furnace. 1

In the drawings: V

Fig. 1 is a diagrammatic showing of my invention embodied in a control system applied to a vapor generator furnace utilizing hog fuel.

Fig. 2 shows a modification of a portion only of Fig. 1.

Fig. 3 illustrates a portion of. Fig. 1 with my invention applied to a stoker-fired furnace. Fig. 4 shows a furnace for the smelting of black liquor.

Fig. 5 illustrates the invention applied to a fluid fired furnace.

In Fig. 1, I have illustrated, in somewhat diagrammatic fashion, my invention applied as a control system to a vapor generating unit heated I by the products of combustion of a solid fuel, such as wood waste products, commonly known as hog fuel. In the other drawings I have illustrated only a portion of the complete system, feeling that it is unnecessary to duplicate'in each of the figures the elements of Fig.1 which are common to all of the figures. Fig. 2 illustrates the furnace of Fig. l in which the brilliancy within the furnace is determined in a slightly different manner than in Fig. ,1. In Figs. 3, 4 and 5 I illustrate'somewhat different furnace structures and the utilization of solid, liquid or gaseous fuels to which the-invention may be applied in a manner somewhat similar to that illustrated completely in Fig. 1, and which will be described in detail.

Referring now particularly to Fig. 1, I indicate 3 Claims. (Cl. 236 -14) 2 I 1 Fir, hemlock, spruce, shavings, bark and other varieties of waste wood fuel differ as to size, B. t. u. content, moisture content, etc. Bagasse is the term commonly given to the refuse of sugar cane, sugar beets, grapes, olives, etc. after the juice has been extracted. Particular features, or characteristics of this general classification of fuel provide problems peculiar thereto, such forexample as wide variations in size and shape of the particles, of the moisture content, of the. B. t. u. value, the volatility, ignition temperatures, etc The lack of uniformity of these variables, even when supplying one particular fuel, presents problems in the control of the apparatus to which my invention is directed. All of the fuels mentioned, however,

' have substantiallythe same variable character- I might be aconstant speed driving engine with a controllable variable speed reduction device between the motor and the screw 6. I

. As the hog fuel drops into the furnace I from the spout 5 it builds a pile or cone 4 having a slope determined by the angle of repose of the particular material. The base of the cone preferably completely covers the grates 9 through which is supplied forced air for combustion. Thisforced draft is availablethrough a duct H] from a constant speed forced draft fan II and the admission rate is varied through the agency of acontrollable damper l2. 1 In normal operation combustion occurs principally over the surface of the cone. The interior of the cone will be composed of a mixture or of at i a furnace of Dutch oven construction from which the hot products of combustion 2 pass to and through the gas passages of a vapor generator 3 for producing steam. Within the furnace l is a pile or cone, of What is commonly termed -hog'fuel. Such fuel may be wood waste, b'aga'sse,

or the like. Wood products may be offvarying i es fro sawd t to. slu s or c p ens, eer};-

strata of ash,- glowing embers and particles of, the hog fuel in various stages of drying. As the raw fuel is dropped upon the apex of the cone and casing outer surface, as well as from the glowing or partly burning submerged. particles.',"',flihe vapors andgasessq expelled ,passjf'outwardly through the'sur'face of the cone'wherefthe volatiles'are. ignitedv and promote the, "combustion 3:91? th ai erjissfrewiies sw me e Ki 3 outer surface. In normal operation the process is self-sustaining with the drying of the fuel and the combustion of the distillates and fixed carbon progressing.

For a uniform rate of fuel supply an increase in the application of forced draft through the ates Q' willrtend wto; blow up the. :fire,;'not only through: the additional percentage ofifreeioxygen in the air, but also from the increased velocity thereof, providing better contact with the ma terial and consequent scrubbing action and also providing better mixture with the dist'rllates. Usually variation in rate of supply of forced draft is highly responsive and sensitive-zandsmay not products of combustion leaving the cone is prefrerable.

tuornforace'rtain fuels a response to brilliancy of the cone surface is preferable, while under other con- ,;ditions a response to brilliancy of the flame or Regardless of the origin of the brilliancy vari- ::able-I.desirably-utilize it as a modifying control be used as a primary control. T:Incdthermrords myeinrconj u c n a p y Control in accordif a. control of the rate of supply of forced draft through the grate is depended uponlto maintain desired steam outflow and steam pressurefrom the vapor generator, overshooting andi'hunting 'will occur, for relatively slight variations in such rraatecofesaidsupply. will: producea .greatersvaria- "tionin: the rate. ofheatliberation, in; thelfurnace. have found'that .a control of thereto or supply forcedldraft fmustithereforebaof a.secondary .".-.Ii:'a.ture.arid ..not..preferaloly be .Zthe; primaryecontrol of the output of thelvapor generator.

.eOn the :other- .hand,. for av .r'elatively uniform .;rate.of.. supplyof forced. draft, a-decreaselinLthe mate .of supply ofr.rawlfu'el will ..'allow the cone .;height.to :ldecrease sand shortly the resistance *fli'heredf to .passage.. or. forced draft, .williidecrease v'vith -;cnsequent blowing. of holes g'through gsthe -:,cone:a1id,progressivelypoorer operation. inucrease in thelrate vjof .supblyof ,hogQiiuel will tend to submerge the..surface1o'f.,the .cone with a. relamlyjgreen or..wet blanket; tending to. smother ""ithelfite, resulting; in smokiness, a'idarkened fur- ..gnace-aridggeneral cooling .of the .entireflfurnace. "Obviously this can be carriedftoLthe "extreme where then fire is completely.- smothered out; by lithr8finfilh0l5fl hogifuel.

At a substantially uniform desired steamrpiessure the-rate of steam outfiow..is'representative ftheid'emand or otthe rate of-heat" output'of' the .naporigenerator. Desirablythe'rate of;heati nput .resnond tothe rate of. heat demand.

iPreferabLv "then; I .control. the": rate of: supply glofhp 'iuel tolthe furnace pri-marily in accordance ance with demand upon the unit. Specifically, I ...primarily utilize rate of steam outflow from the "vaporgenerator-as a primary control, modified by 13";1116315111'9 of brilliancy within the furnace, to

conjointly eifect a control of the rate of supply functions:

ll-nAcontrol. ofltheinduced draft (-rate of discharge of,..produ'ctsi.ofcombustion from the'fur- .naceand .vapongenerator) -inlaccordance with a .determinationoflthepressureat a preselected 10- cation in Lthelunit. iscommonly termed'ffurlnacefdraiit control and serves .to minimize infiltration of. airilthrough 'thesettingor leakage of gaseons. products outwardly through the setting.

24A .controhof the .rate of air admission T3135" throughthe grates. in. accordance with pressure of the steam leaving the vapor generator.

3..;A,.control of the speed or the screw feeder fian'dt thereby a control of volumetric rate of supplygof hog fuel'to the furnace, conjointly from ..a.continuous determination'of rate'of vaporv outflow'(representative'of demand upontthehunit) and .fr,0m brilliancyat a preselectedlocation Within the furnace.

I iridic'ateiati' l3 a constant speed induced draft 1 'fan"drawingtheproducts -of combustion from to the "generator" (from the;furnace)"s'hould corthe unit and discharging them to a stacker other- Wise. "'Controlof the rate'of flowof suchproducts of combustion from the. furnace ishad: bya positioningiofadamper HI inan outletduct 15. The

".Witlftherateofyaporoutfiow,fromfthe generator ,L'damPerFTis' arrangedto bepositionedby a-pneuisilchwontrokihowever, is not the completeanswer, tiforreaizhltxirbic'lfoot,of hogifuelusupplie'd.xvill vary zsomewhatas todensity, moistureicontentiBi tilll. iiialue,volatilitlniixd carbon; etc..ffEachofthese f'yariables contribute to the: .extent' to which the enveloping 'surface'pf'raw fuel tends: toismother .iorndarkenwtheucombustion iabout' thepouter sur- Liane ,of,the' cone. jIi haveflfound thateven though if dingicontinuously asing1e'"class of fuelfsuch fffori. example as "firrefuse,the minuteby minute .variation' 'in size;1moisture'content," etc. produce 'yariations in thesmothering effect. "Forexample, gthet'firi hog? fuel "may -yary" in size i from sawdust 'ltd largebhips orbhunks; The-moisture content amd volatizing characteristicsfwill vary between -woodland?barkiparticles; while jtheB. t. u. con

" :maticzcoritroller l6. :having a diaphragm I 1' sen- "sitivetoitheitfurnacedraft or pressure at a seflectd location, for example 8, within the unit. The'loca'tion i 3*is" usually oneat which it is desired'to: maintain substantially atmospheric pres- ":surethroughthe: control'of rate 'of suction of the iigaseousf products through thej'duct H: in accordance With'rate ofsupp'ly of'said gaseous products "'fromithe' furnace I. Such-control provides a 11111- tary systemwith usual ad-justab'le features where- .in the/furnace draft may' be continuously main- .tained'as' desired.

"In controlof'the rate ofsupplyof'air for combustion' through the positioning of i the damper L:'I2"I indicate'apneumatic-controller I9 responsive to'acontinuous measure'of pressure of the steam leaving the generator '3.Connectedto the "steam 'outfiow main 20' 'is a'pipe 2 l communicat- "ing"withfihe interiofof a B'ourdon' tube' Z 2 which is arrang'd' to "position" the' movableel'ement :ot a

770 I pilot=va1ve 23'; thereby establishing a' loa'ding pres :sureiin' the pipe" 24. continuouslyrepresentative: of '75. e*valuefof 'steam,'ipressure. iThe el'ements are justab1e irrknowmmanner so th'at a given range steampressure values -may-"result im a pre'defed; Such arriri'tficati on isthebrilliancy'of thei flfiem nd rang in di p s u s i t i grate 9.

24. Preferably this control is relatively insensitive, for as previously mentioned the combustion nace I. Superimposed in the pipe 38 is a selector valve 40 similar to the selector valve 21 and i allowing manual control of the rheostat 8 if desired.

In general, I provide a control of induced draft to maintain furnace draft value as desired. The supply 'of air for combustion is under the control of vapor outflow pressure. The volumetric rate of supply of hog fuel to the furnace is continuously proportioned to the vapor outflow rate and is continuously modified in accordance with a measclosed and claimed in the patent to Gorrie Re.

21,804, continuously establishing a control pressure in the pipe ZBleading to the pneumatic controller l9. Superimposed in the pipe 26 is a selector valve 21 providing the possibility of removing control of the damper l2 from automatic response to steam pressure variations and allowing remote manual positioning of said damper if desired.

I indicate at 28 a steam flow meter continu-, ously responsive to the weight rate of flow of steam discharged through the conduit Zllto any point of usage. The meter 28 is arranged to position the movable element of a pilot valve 29. thereby continuously establishing in a pipe 3!! an air loading pressure representative of the weight rate of vapor leaving the vapor generator and thus continuously representative of the B. t. u.

demand upon the unit.

At 3| I indicate a brilliancy meter cormected by the necessary electrical leads 32 with a sighting arrangement 33. The sight 33 is (in Fig. 1) preferably shown as sighting through the flame and gaseous products of combustion leaving the Dutch oven l. However, under certain conditions it may be preferable to sight the unit 33 directly at the surface of the cone 4 or at the walls of the furnace (Fig. 2). In any event the sighting unit 33 includes a photo-voltaic cell sensitive to brilliancy at a predetermined site within the combustion chamber and continuously establishing a direct current E. M. F. representative of a measure of brilliancy at desired location.

The brilliancy meter 3! is of known type, sensitive to a small value direct current for positioning the movable element of a pilot valve 34. thereby continuously establishing in the pipe 35 a loading pressure representative of a brilliancy factor within the furnace l.

Within the pipe 35 is a throttle valve 36. The 0 loading pressures within the pipes 30 and 35 are applied to opposing chambers of an averaging relay 3?, which may be of the type described and claimed in the Dickey Patent 2,098,913. A control pressure is continuously established within a pipe 33, the resultant of the pressures applied to the averaging relay 31. The throttle valve 36 is so adjusted as to vary the relative effect of the loading pressure from the brilliancy measure. In other words, I may so adjust the system that the loading pressure within the pipe 38 is a composite of 80% steam flow effect and brilliancy effect, or I may vary the relative effect of the two controls as desired. As previously mentioned, the primary control is in accordance with the continuous measure of B. t. u. demand upon I the unit modified by an indication of brilliancy within the furnace l, which is indicative of variations in moisture content, volatility, B; t. u. content, etc.,'of the fuel being supplied.

The control pressure established in the pipe 38. is applied to a pneumatic controller 39 for positioning the rheostat 3, thereby controlling the speed of the feeder screw 6 and consequently the volumetric rate of supply of raw fuel to the furure of brilliancy within the furnace. Thus I primarily proportion the B. t. u. input to the furnace to the B. t. u. demand upon the unit but through the modifying or readjusting control from brilliancy I take into account variations in the fuel, such as moisture content, B. t. u. content and the like which would otherwise make slightly incorrect the volumetric measure of B. t. u. supplied to the furnace.

In Fig. 2 I show a modified control wherein the brilliancy sight is aimed to be directly responsive to brilliancy of the cone surface.

While I have described the arrangements of Figs. 1 and 2 in connection withv the burner of hog fuel, bagasse and similar materials, it will be evident that the control of combustion from a measure ofbrilliancy is not limited thereto, but finds useful application in combination with aparatus for burning other fuels, such as coal or coke in a fuel bed or fluid fuels forced into a furnace. By fluid fuels I intend to include such fuels as pulverized coal, oil, gas, blast furnace gas,

black liquor, and the like.

In Fig. 3 I indicate a furnace having a solid fuel bed 43 of coal upon a grate 44 to th underside of which is applied forced draft. The brilliancy sight 33 may be sighted at the surface of the rate of fuel supply to the bed.

Referring now to Fig. 4, I show therein a furnace for the reduction and smelting of black liquor, or in general to the treatment of waste liquors from chemical methods of treating wood or like material in the production of pulp or paper, and is particularly directed to the recovery of chemical and heat values from such liquors.

In th treatment of cellulosicmaterials for the production of pulp, particularly by alkali chemical methods, the waste liquors usually known as 1 black liquor, contain valuable chemical and heat I generating constituents, the recovery of which'is of great economic importance. After certain evaporative operations the concentrated liquor is usually sprayed into the smelting furnace, on the bottom of which the blackash is burned by the introduction of air, and excess air introduced completes the oxidization or combustion of any gases'not completely oxidized in the smelting zone. The heat thus generated, causes the vaporization of the liquor and the completely burned liquid, sludge, and finally by partially dried fra generation of steam and like purposes.

Referring to Fig. 4, the concentrated liquor is] sprayed inithe: usual manner through the wall of spray nozzles, and these are preferably directed; atv least in part, against the walls of the furn-acej so that the walls are coated in varying degree b ments 46 which collect and eventually drop to tli bottom of the furnace, forming a semi-plastic bed 41. The bottom of the furnace is usually sloped messages within th rfurnacevizisithecbest criterion sofa-opertationewithni theiurnace.

'iIniFigfiwLindicateuthat afurnaee'ma nbe"siup- :plied,with a gaseous 'or fluidyfuel throng-broiler or more burners E9. The burner orburnerszrmay be sslocated in commonrnanner andznray supply such rfluid: fuels as pulverized coal, :;blast furnace -gas, oil, or the like. oaThe nbrilliancyesightfia;may be cdirected acrossithe flame or at one of the furnace .=w-a-lls as found: mostadvantageous, and:the meas- :smixture. v

JIta-i e a; principal -object 10f my invention to aincorpor-atei the combustion variable'rbrilliancyi in carcontrol of: One.'01"K10131015 the"e1m6ntSIDf3COl'ilbustion,-and such method ma beaccomplished "through-a manual; control of the element -or::eleiments-rof icom-bustion from. an observation of a 'brilliancy meter and of other-meters: as disclosed, 501*:1 11 ma .be accomplished automatically.

' WhiIe I shave -disclosed and described certain rpreferred embodiments ofrny; invention; it is tobe sunderst-ood'that I-dothis byrway'of example only rand not iinallimiting manner.

-What I .claimvas new and-desire to; secure by :Letters Patent of the United States is:

1. The method of operating a'hog" fuel fired evapor generator.- he'atedzby products "'OfTCOIIlbHS- tion occurring in a furnace, comprising :forming ;;a=- conicalbed of said fuel, supplying 'fuelzto'the stop portion of said bed, separately and continuous;ly"supplying air for; combustion to the furnaceubeneath said bed, continuously controlling In general ,;the arrang em ent-lprovid es vapors generator heated :by rproductsmf: combustion occurring. inza:furnace,:comprising;iorming a conical bed :of said:fuel,: supplyingsfluel-ato ithe top portion of saidbed, separatelyr-supplyingaair for combustion to' thesfurnace' beneath saidxbed, continuously controlling the supply of air'forrcombustion responsive to the. pressure of r the generated vapor, continuously determining: therbrilliancy of the combustion abou't theoutersuriace of said conical bed, determining thearatepfflow of generated vapor, controlling thei rateof' 'tuel supply primarily in accordance with 2 the :rateiof flow of generated vapor tolincrease theirateiof fuel supply as the' flow-of generated vapor increases, and continuously modifying the controlling of the rate of fuel supply in-accordance with :eureref 'br-illiancyutilized in control of; the aiir fuel ,l the discharge ofthe products of :combustion'from t-he :iurnacecresponsive .to: draft-:through the fur- .nace, continuously; controllingithmsupply .of" air .lfor'zcombustion responsive" totthe pressure "of the *generated" vapor, continuously "determining? the "ibrilliancy of the surfaceofsaid conical bed,continuously idetermining the rate of xfiowv of -generated' .vapor, :continuously: controlling the rate for fuel: supply primarily 'in' accordance :With" the rate :of alowiof'lgenerated'vapor by increasing'the rate of'fuel'vsupply as the flow of generated vapor'inncreases, and'continuously. modifying the controliiling'of the rate offuel'supply in accordance with ."isaid'idetermination of brilliancy to 'maintain'a ripredetermine'dstandard and in a direction'tendwing to reduce the rate of'fuel supply as the brilliancy decreases from saidpre'determine'd "standard,"and vicer versa.

2. The method of; operating a: hog fuel 'fir'ed said determination of brilliancy to-maintain a predetermined standard and-in a 'directionto reduce the rate of fuel supplyeas'the br'illiancy decreases, and conversely. I

3. Apparatus for controllingthe operation of ca hog fuel fire'd va'por'generator, "comprising in combination, a iurnace provided wlth grates adapted to'burn hog fuel, feed means contin-uously discharging such fueldownwardlyinto the furnace arid-on to the grates-at-a' variable rate to build a cone shaped'iuelbed, means supplying air for combustion to the furnacebeneath the grates, means continuously responsive to 'vapor outflow; pressure to -=continuously -regulate the means supplying air for combustion; a'd'evice continuously responsive'to rate of vapor outflow from the generatonbrilliancy responsive means including a brilliancy sight arranged to seethe'brilliancy "of combustion about the outer surface of *said fuel and a brilliancymeter'continuously responsive to said sight, and means continuously-actuated by said vaporoutflow responsive device'to increase the rate of fuel discharged-bysaid feed meansas the flow of; generated vapor -increases, said continuously actuated means being conjointly and continuously actuated-by said 'brilliancy responsive-means in a direction to reduce said rate of fuel discharged-as the brilliancy decreases from a predetermined standard-a-ndconversely.

HAROLD T. SAWYER.

REFERENCES I CITED The following ref erencesuare of Hrecordins the file, of this patent:

UNITED STATESIPATENTS Number Name .Date Re.:19,592 Gibson May 28,- 1935 1-,3385928 Hopwood 'May l, 1920 1,471,342 Logan Qct. 23,1923 1,729,701 Bennett --.Oc't.;1, 1929 1,906 244 Benjamin --May. 2,- v1933 ..-.2,143,320 Payn Jan.- 10, v1939 OTHER REFERENCES Volbrath; pages 15, 16 andil'? ofl:nstrumenta- 'tion, October and November issue, 1945, "pube lished by Brown Instrument Gompany, Philadelpl1ia,IPennsylvania. 

